1. Field of the Invention
The present invention relates to a mobile ballast cleaning machine mounted for mobility in an operating direction on a track consisting of rails fastened to ties to excavate ballast supporting the track, to clean the excavated ballast and to redistribute the cleaned ballast under the track. The machine comprises a machine frame supporting a ballast excavating and conveying chain having a section passing transversely under the track for excavating the ballast at an excavating site, a screening installation arranged to receive the excavated ballast from the ballast excavating and conveying chain and to separate waste from the excavated ballast to produce cleaned ballast, a cleaned ballast redistributing apparatus arranged to receive the cleaned ballast from the screening installation and to redistribute the cleaned ballast at a ballast discharge site behind the ballast excavating site, and a cleaned ballast compacting device.
2. Description of the Prior Art
Such a mobile ballast cleaning machine has been disclosed in U.S. Pat. No. 4,355,687, dated Oct. 26, 1982. In this machine, the cleaned ballast leveling and compacting device is mounted behind the cleaned ballast discharge site and comprises a leveling device including a pair of endless ballast leveling chains for distributing the redistributed cleaned ballast over the ballast bed and for leveling the distributed cleaned ballast, a vertical pivot supporting each endless ballast leveling chain for pivoting inwardly from a respective ballast bed shoulder in a plane underneath the track, a rotary drive for driving each ballast leveling chain, and a power drive linking each ballast leveling chain to the machine frame for vertically adjusting the ballast leveling chain. The power drive is connected to a parallelogram guide mechanism mounting each ballast leveling chain on the machine frame for horizontal and vertical adjustment. A ballast compacting device is arranged rearwardly of the ballast leveling chains in the operating direction and is comprised of a vibratory beam extending transversely to the track and having respective ends preferably resiliently connected to elongated carriers at the respective sides of the machine frame. The unevenly discharged cleaned ballast is leveled by the leveling chains and the leveled cleaned ballast is then compacted by the vibrating beam engaging the surface of the leveled cleaned ballast. This leveling and compacting device takes up a considerable amount of space since it is comprised of separate leveling and compacting units and often requires a rather high track lift since the two vertically adjustable units are positioned between the level of the cleaned ballast bed and the track. On the other hand, the ballast compaction is not always sufficient since the unevenly distributed cleaned ballast causes gaps in the ballast bed. This is of particular disadvantage where these gaps occur at the points where the ties are supported on the ballast.